1. Field of the Invention
The present invention relates to the field of use of suspension systems for bicycles. More particularly, the present invention relates to a device for locking and unlocking bicycle suspension systems.
2. Description of Related Art
Bicycles are two-wheeled vehicles designed to carry a rider (i.e., a "cyclist") over many types of surfaces. Specific adaptations of bicycles designed to handle rough terrain, known as "mountain bicycles", or "mountain bikes", usually have to travel over obstacles such as rocks, and logs, and also surface irregularities such as dips and holes. To enable better handling of mountain bikes and offer smoother rides to cyclists, suspension systems have been added.
These suspension systems typically include a liquid filled shock absorber and a coil spring disposed around the shock absorber. For a rear wheel suspension, the shock absorber/coil spring assembly is usually mounted between the main frame of the bicycle and the rear wheel support frame.
FIG. 1 illustrates a side view of the rear portion of a prior art mountain bicycle 2 having a main frame 4 with a seat post 5; a rear wheel support frame 6 for holding a rear wheel 8; and a suspension system 10 including a swing arm 12 pivotally connected to rear wheel support frame 6 and seat post 5 at pivot points 14 and 16, respectively; and a shock absorber/coil spring assembly 18 having a coil spring 20 and a shock absorber 22. The shock absorber/spring assembly 18 is pivotally connected to rear wheel support frame 6 and swing arm 12 at pivot points 24 and 26, respectively.
In FIG. 1, the path of travel of pivot point 14 is illustrated by a motion line 28. Also, the compression and expansion of shock absorber/coil spring assembly 18 (i.e., coil spring 20 and shock absorber 22) are illustrated by compression arrows "A'" 32 and expansion arrow "B'" 30, respectively.
When rear wheel 8 encounters an obstacle such as a log or a rock, causing rear wheel 8 to exert a force upward against rear wheel support frame 6, pivot point 14 will travel along path 28 in direction "A". As rear wheel support frame 6 is thus deflected, shock absorber/spring assembly 18 will be compressed as shown by compression arrows "A'" 32.
Conversely, when rear wheel 8 encounters a surface irregularity such as a hole or a dip, the expansion action of spring 20, as indicated by expansion arrows "B'" 30, will cause pivot point 14 to travel in direction "B" and rear wheel support frame 6 to travel in a downward direction.
As discussed below, shock absorber/coil spring assembly 18 can also be caused to compress and expand as illustrated by compression arrows "A'" 32 and expansion arrows "B'" 30, respectively, when, on smooth surfaces or riding uphill, a cyclist is exerting force on the pedals (not shown) to propel the bicycle. As a result, dipping would occur and efforts of the cyclist would also be inefficiently expended unnecessarily.
The oscillation of suspension system 10 occurs when a cyclist is riding on a smooth surface such as a paved road, as the pedaling motion of the cyclist will cause these suspension systems to oscillate. This oscillation effect is known as a "dipping effect", and results in the absorption of the pedaling efforts of the cyclist. The dipping effect occurs when suspension system 10, reacting to the forces exerted by the cyclist's pedaling motion, absorbs energy which otherwise would be put into propelling the bicycle.
Another problem with suspension systems such as suspension system 10 occurs under situations where the surface of the terrain is of a certain irregularity. Under these situations, suspension system 10 can also begin to oscillate. In cases where the oscillation becomes very great, loss of control of the bicycle by the cyclist can result, which in turn can cause serious injury and damage to both the cyclist and other property.
One solution that has been proposed for the problems mentioned above is to "lock out" or disable the rear suspension system in situations where the suspension system might interfere with the most efficient operation of the bicycle. These include the above-mentioned cases of smooth surface riding and also uphill riding.
One implementation of the solution is by inhibiting fluid flow between two or more chambers of a shock absorber contained in the suspension system (e.g., shock absorber 22), with the inhibiting device being integral to and located in the shock absorber. The control of the inhibiting device is achieved through the use of a cable connecting the inhibiting device and a lever mounted on the handlebars of the bicycle.
One example of this solution is contained in U.S. Pat. No. 4,582,343, "Light Weight Rear-Wheel Bicycle Suspension", issued to Waugh, on Apr. 15, 1986 (hereinafter Waugh). The device of Waugh contains a spring-loaded hydraulic shock absorber for damping the relative movement of a rear wheel of a bicycle. The hydraulic shock absorber incorporates a rider-controlled valve for hydraulically locking and unlocking the shock absorber, allowing the rear suspension to function both in a suspended mode and a rigid mode.
Other patents which have been issued and are directed at the same general concept include: U.S. Pat. No. 4,989,698, "Control Device for a Lockable Gas Spring", issued to Dony, on Feb. 5, 1991 (hereinafter Dony); and U.S. Pat. No. 5,320,375, "Interruptable Shock Absorber Suspension for Bicycles", issued to Reeves et al., on Jun. 14, 1994 (hereinafter Reeves).
Although the devices disclosed in Waugh, Dony, and Reeves function to inhibit the operation of a suspension system of a bicycle, to implement them would require extensive modification and/or the redesign of shock absorber 22 to include many parts. In addition, all three devices require a cyclist to actively sustain the inhibition of the suspension system--i.e., the cyclist must exert constant pressure on the lever mounted on the handlebars to control the inhibition of the operation of the shock absorber and thereby the suspension system.
Another solution that has been proposed is contained in U.S. Pat. No. 5,354,085, "Sprung Bicycle", issued to Gally, on Oct. 11, 1994 (hereinafter Gally), which is directed to a bicycle having a locking device for a suspension system where the locking device is being automatically actuated by a driving-force sensor. However, the Gally device also suffers from the same disadvantages as the Waugh, Dony, and Reeves devices as it also requires that the inhibiting device be located inside the shock absorber. In addition, the Gally device suffers from the additional disadvantage in that a cyclist cannot manually engage/disengage the inhibiting device, thereby preventing the cyclist from having full control of the inhibiting of the suspension system.
Therefore, what is desired is a device for inhibiting the operation of a suspension system which can be engaged and disengaged, as needed by a cyclist, and which does not require extensive modifications to existing suspension systems nor require the manufacture of complex assemblies.